Rejuvenation of the kind that Miller discovered continually restored the innocence of the individual. Mice could cope with that kind of continual loss, because they could learn everything they needed to know to get along as mice over and over again. Higher mammals couldnt; even dogs rejuvenated by the Miller technique
were reduced to helpless imbecility, unable to learn as quickly as their learning evaporated. That was why rejuvenation research in the following century had been concentrated on more selective and more easily controllable Internal Technologies: technologies which my generation were the first to exploit on a wholesale basis.
People of my generation had hoped maybe even expected that nanotech systems would continue to improve as we got older, so that every extra decade of life we obtained would produce further rewards. What the history book told me now, though, was that the escalator had run into the law of diminishing returns.
Two hundred years of life became routine, three hundred just about possible for the very rich and the very lucky. Damons three-hundred-and-thirty-some year span had been highly unusual even for members of the Inner Circle. Repairing the body parts below the neck had not been unduly problematic in the majority of cases, although periodic invasive and incapacitating deep-tissue rejuvenations had been required to support the routine work of IT repair, but keeping the brain going without destroying the mind within had proved much more difficult.
The menace posed by Millerization had been complemented soon enough by robotization: the loss of a brains capacity to further refine its neuronal configurations. Carefully protected from the obliteration of memory and personality, the brains of men of Damons generation had tended to the opposite extreme, settling into a quasimechanical rut which made them incapable of assimilating new experiences or reformulating their memories. Attempts had been made to get around this problem by means of inorganic augments meatware/hardware collaborations involving various kinds of memory boxes but none had succeeded in forging a workable alliance and most had exaggerated the problems they were attempting to solve.
The advent of the Zaman Transformation, which involved engineering fertilized ova for extreme resistance to the aging process, had not only sidestepped many of the problems associated with IT repair systems but had appeared to strike a balance in the brain between Millerization and robotization. The neurones of ZT brains retained a greater capacity for self-regeneration than the neurones of ordinary mortals, but they retained the switching capacity that permitted rapid learning. Although the first generations of true emortals could keep a firm enough grip on their memories and learned skills, they seemed to be equally capable of further adaptation. Their memories of times past became increasingly vague, but never lost their coherence, while their capacity to assimilate new experience remained undiminished or so, at least, the argument went.
Not everyone, it seemed, was convinced.
Many people believed that robotization remained a threat and that many living individuals had, indeed, been robotized, although they retained the illusion of being fully human and continued to maintain that appearance. Opinions differed, as one might expect, as to exactly which individuals might have become existentially becalmed in this way.
On the other hand, many people believed that the bugbear of Millerization had not been entirely overcome, and that the real existential threat facing the new emortals was not mental petrifaction but a loss of the continuity of the self: too much change rather than too little.
Some people, of course, believed that both processes were observable in the world around them usually, but not necessarily, in different individuals.
At any rate, the quest for a perfect mental balance within a brain whose developmental course avoided both the Scylla of Millerization and the Charybdis of robotization had not been abandoned once Zaman Transformations became the norm. Far from it. All kinds of research were continuing, based in many different theories and ideologies.
So-called cyborganizers had resuscitated many formerly abandoned lines of research into meatware/hardware collaboration, while Zamaners including those sponsored by the Ahasuerus Foundation had hardly paused to draw breath before producing hundreds of variations and refinements of their basic technique. The situation had been further complicated, it seemed, by a leap forward in the field of genomic engineering following the discovery elsewhere in the galaxy of natural genomic systems differing quite markedly from the one that was fundamental to Earths ecosphere.
In brief, there were now many different humankinds and not-so-humankinds, most of which laid claim to sole possession
of the ideal emortality. The people of Excelsior seemed to me to be among the weirder lines in the posthuman spectrum although that was not an impression encouraged by their own data banks but there were undoubtedly others every bit as weird to be found among the fabers of the outer system microworlds and the cyborganizers of the Jovian and Saturnian satellites, not to mention the carefully adapted colonists of Ararat and Maya.